Drill, drilling unit, and drilling method

ABSTRACT

According to one implementation, a drill includes: a body without a back taper and a cutting edge part. The body has a flow path of a cutting oil. The flow path is branched to first and second flow paths inside the body. The cutting edge part has a first supply port that supplies the cutting oil toward a workpiece. The first supply port is an outlet of the first flow path. The body has a second supply port that supplies the cutting oil to a clearance between the body and a bush for positioning the body. The second supply port is an outlet of the second flow path. The second flow path has a pressure loss by which the cutting oil is not scattered from the second supply port in a radial direction of the body but exuded from the second supply port.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2018-231043, filed on Dec. 10, 2018; theentire contents of which are incorporated herein by reference.

FIELD

Implementations described herein relate generally to a drill, a drillingunit, and a drilling method.

BACKGROUND

Conventionally, a drilling method using a drilling jig, such as adrilling plate and/or a guide bush, is known as one of drilling methods.As a specific example, a drilling method for deep hole processing withhigh precision using a guide bush, which can supply cutting oil inside,has been proposed (for example, refer to Japanese Patent ApplicationPublication JP2015-120216 A).

In drilling using a drill, supplying cutting oil leads to improvement indrilling precision and a tool life. Accordingly, a technique to form aflow path of cutting oil inside a drill to supply the cutting oil towarda workpiece from a cutting edge of the drill is known. As a specificexample, a drill in which discharge ports of cutting oil have beenformed in cutting edges in addition to lands has been proposed (forexample, refer to Japanese Patent Application Publication JP2009-83092A).

An object of the present invention is to allow drilling with higherprecision in the case of drilling by inserting a drill into a guidebush.

SUMMARY OF THE INVENTION

In general, according to one implementation, a drill includes: a bodywithout a back taper and a cutting edge part. The body has a flow pathof a cutting oil inside. The flow path is branched to a first flow pathand a second flow path inside the body. The cutting edge part isintegrated with the body. The cutting edge part has a first supply portthat supplies the cutting oil toward a workpiece. The first supply portis an outlet of the first flow path. The body has a second supply portthat supplies the cutting oil to a clearance formed between the body anda bush for positioning the body. The bush is used by inserting the bodyinside the bush. The second supply port is an outlet of the second flowpath. The outlet of the second flow path is formed on an outerperipheral surface of the body. The second flow path has a pressure lossby which the cutting oil is not scattered from the second supply port ina radial direction of the body but exuded from the second supply port.

Further, according to one implementation, a drilling unit includes theabove-mentioned drill and the bush.

Further, according to one implementation, a drilling method forproducing a drilled product includes: using at least the above-mentioneddrill and the bush for drilling the workpiece; and supplying the cuttingoil.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 shows a structure of a drilling unit including a drill accordingto the first implementation of the present invention;

FIG. 2 shows a state where the drilling unit shown in FIG. 1 is drillinga workpiece;

FIG. 3 shows an example case of drilling using the conventional straightdrill having a back taper and the guide bush;

FIG. 4 is an enlarged vertical longitudinal sectional view showing astructure of the body composing the drill according to the secondimplementation of the present invention;

FIG. 5 is a right side view of the body shown in FIG. 4;

FIG. 6 shows a structure of a drilling unit including a drill accordingto the third implementation of the present invention;

FIG. 7 shows a state where the drilling unit shown in FIG. 6 is drillinga workpiece;

FIG. 8 is a longitudinal sectional view of the body showing an examplecase where the through hole for inserting the member shown in FIG. 6 isblockaded with the plug member;

FIG. 9 is a longitudinal sectional view showing an example case wherethe drilling unit is composed by an insert drill of which body hashelical flutes and cutting edges can be exchanged;

FIG. 10 is a longitudinal sectional view showing a state where thedrilling unit shown in FIG. 9 is drilling a workpiece;

FIG. 11 is an enlarged vertical longitudinal sectional view near the tipof the insert drill shown in FIG. 9;

FIG. 12 is a longitudinal sectional view showing an example of structurein the cutting edge part of the insert drill shown in FIG. 9;

FIG. 13 is a perspective view showing the first structural example of amember inserted into at least one through hole formed in a body of adrill according to the fourth implementation of the present invention;

FIG. 14 is a perspective view showing the second structural example of amember inserted into at least one through hole formed in a body of adrill according to the fourth implementation of the present invention;and

FIG. 15 is an enlarged partial sectional view of the body and thecolumnar member, showing an example in which a clearance formed betweena male screw and a female screw is used as the second flow path.

DETAILED DESCRIPTION

A drill, a drilling unit, and a drilling method according toimplementations of the present invention will be described withreference to the accompanying drawings.

(First Implementation) (Structure and Function)

FIG. 1 shows a structure of a drilling unit including a drill accordingto the first implementation of the present invention. FIG. 2 shows astate where the drilling unit shown in FIG. 1 is drilling a workpiece.

A drilling unit 1 drills a workpiece W using a handheld drill drivingdevice, having at least a rotor for rotating a desired cutting tool. Thedrilling unit 1 has a drill 2, a guide bush 3, and a drilling plate 4.The guide bush 3 is used for positioning the drill 2, by being insertedinto a through hole, for positioning, formed in the drilling plate 4 oranother drilling jig.

Since the drilling plate 4 should have a structure to be easily placeddepending on the structure of the workpiece W, it is often appropriatethat the drilling plate 4 is produced by a user of the drilling unit 1.Therefore, the drilling unit 1 may be composed of the drill 2 and theguide bush 3, without the drilling plate 4 being an element of thedrilling unit 1. The drilling plate 4 shown in the figures has astructure in which a through hole for inserting the guide bush 3 hasbeen formed on a platy member. The guide bush 3 inserted into thethrough hole of the drilling plate 4 is fixed to the drilling plate 4 bya setscrew 4A.

The workpiece W is a laminate material composed by overlapping threeplate materials W1, W2, and W3. As a specific example, the workpiece Wcomposed by overlapping the plate material W1 made of CFRP (carbon fiberreinforced plastics), the plate material W2 made of aluminum, and theplate material W3 made of titanium can be an object to be drilled by thedrilling unit 1. As a matter of course, a laminate material, a simpleplaty portion, a block-shaped portion or the like, each made of a samematerial, such as a metal or a composite material, can be an object tobe drilled by the drilling unit 1.

The drill 2 has a body 5, without a back taper, and a cutting edge part6 forming the desired number of cutting edges. The drill 2 held by ahandheld drill driving device or the like is also called a drill bit inorder to distinguish from a drill driving device. One end of the body 5is used as a shank 5A for holding the drill 2 with a holder of a drilldriving device while the other end of the body 5 is integrated with thecutting edge part 6. At least the cutting edge part 6 side of the body 5without a back taper has a constant diameter, and is inserted into theguide bush 3.

In the example shown in FIG. 1, the diameter of the cutting edge part 6is longer than the diameter of the body 5. Therefore, the guide bush 3has a cylindrical structure having a step through hole consisting of thefirst hole, having the first diameter, which guides the cutting edgepart 6 in the workpiece W side, and the second hole, having the seconddiameter smaller than the first diameter, which guides the body 5 on theopposite side of the workpiece W.

Since the guide bush 3 is used by being inserted into a through hole forpositioning formed in the drilling plate 4 or the like, the outline ofthe guide bush 3 in the workpiece W side is determined so that thetolerance between the outline of the guide bush 3 in the workpiece Wside and the diameter of the through hole for positioning formed in thedrilling plate 4 or the like become a tolerance corresponding toclearance fit.

When a ring-shaped convex portion is formed on an outer surface of theguide bush 3, the guide bush 3 can be positioned in the tool axisdirection by making a ring-shaped stepped surface, perpendicular to thetool axis direction, contact with a surface of the drilling plate 4 orthe like, as shown in the figures. Furthermore, the guide bush 3 can befixed to the drilling plate 4 by holding the ring-shaped convex portionof the guide bush 3 between the setscrew 4A and the drilling plate 4, asshown in the figures.

The cutting edges of the drill 2 may be attached to the cutting edgepart 6 interchangeably. A drill whose cutting edge can be exchanged asan insert or a head is also called an insert drill. When the drill 2 isan insert drill, the body 5 and a portion of the cutting edge part 6except the cutting edges also function as a holder for holding eachcutting edge interchangeably.

A two flute insert, which has been on the market for conventional insertdrills, can also be used as an insert for the drill 2. Therefore, thedrill 2 may be composed of the body 5 and the cutting edge part 6 havinga structure, in which each cutting edge can be attached while anexisting general-purpose insert may be used as the cutting edges.

The diameter of the end portion in the holder side of the body 5, whichis not inserted in the guide bush 3, may be larger than not only theinside diameter of the guide bush 3 but the diameter of the cutting edgepart 6 in order to secure rigidity. In other words, another connectingmember, such as the shank 5A or a screw, thicker than the diameter ofthe body 5 may be coupled to the holder side of the body 5. In thatcase, the drill 2 is a non-straight drill in which the diameter of thecutting edge part 6 is larger than the diameter of the body 5 in thecutting edge part 6 side. Also in that case, the diameter of a portionof the body 5 in the cutting edge part 6 side, which is used by beinginserted in the guide bush 3, is constant.

Regardless of the diameter of the shank 5A, it is appropriate to form aflute or flutes for discharging chips in the cutting edge part 6 side ofthe body 5. For example, helical flutes can be formed in the cuttingedge part 6 side of the body 5 similarly to a twist drill.Alternatively, linear flutes may be formed in the cutting edge part 6side of the body 5 similarly to a straight fluted drill.

The length of a portion of the body 5, having a constant diameterwithout a back taper, is determined so that the drill 2 can be fed outin the tool axis direction. Therefore, the longer the length of theportion of the body 5 without a back taper is, the longer a distancethat the drill 2 can be fed out in the tool axis direction can be.Accordingly, the diameters of the body 5, including a portion used asthe shank 5A for holding with a holder, may be constant as shown in thefigures.

As a matter of course, not only limited to the examples shown in thefigures, the diameter of the cutting edge part 6 may be same as thediameter of the body 5 to compose a straight drill, or the cutting edgepart 6 and the body 5 may be made of a same material to compose a solidtype drill. Also in that case, the cutting edge part 6 side of the body5 does not have a back taper, and a tool diameter is constant.

When the drill 2 is an insert drill as described above, the price of thedrill 2 can be reduced since only a cutting edge made of an expensivematerial, such as carbide or ceramics, can be exchanged when the cuttingedge is worn while the body 5 is made of a cheap material, such ashigh-speed steel, similarly to the conventional insert drill. Sincethere are few straight drills without a back taper in recent years, tomanufacture a straight drill newly requires large scale equipment. Bycontrast, since a holder for an insert drill whose diameter of cuttingedge is larger than the diameter of the holder does not contact with aworkpiece, a holder without a back taper has also been marketed.Therefore, when the drill 2 is an insert drill, the drill 2 can bemanufactured using the conventional equipment as much as possible.

At least one flow path 7 of a cutting oil is formed inside the body 5.The cutting oil is supplied to the flow path 7 in the body 5 from theholder side of the body 5. Therefore, it is practical to form anentrance of cutting oil on an end face in the holder side of the body 5.In the example shown in the figures, the linear flow path 7 of cuttingoil has been formed on the tool axis of the body 5 whose diameter isconstant. In this case, the body 5 has a cylindrical structure.

Note that, the flow path 7 of the cutting oil may be formed at aposition which is not on the tool axis of the body 5. Alternatively, aplurality of the flow paths 7, parallel to the tool axis, may be formedin the body 5.

The cutting oil supplied to the flow path 7 in the body 5 is mainlysupplied from the cutting edge part 6 to the workpiece W through theflow path 7 in the body 5. Therefore, at least one outlet of the cuttingoil is formed in the cutting edge part 6. Each outlet of the cutting oilis used as the first supply port 8A for supplying the cutting oil towardthe workpiece W from the tip of the drill 2. In the example shown in thefigures, the four first supply ports 8A have been formed in the cuttingedge part 6 of the drill 2.

Furthermore, some of the cutting oil supplied to the flow path 7 in thebody 5 is supplied to a space formed between the guide bush 3 and thebody 5. Then, the cutting oil supplied to the space is used forlubrication between the guide bush 3 and the body 5. For that purpose,the body 5 has the second supply port 8B or the second supply ports 8Bfor supplying the cutting oil to the gap formed between the guide bush 3and the body 5.

Accordingly, the flow path 7 of the cutting oil can be branched to thefirst flow paths 7A and the second flow paths 7B inside the drill 2.Thus, the cutting oil can be supplied to the first supply ports 8Athrough the first flow paths 7 while the cutting oil can be supplied tothe second supply ports 8B through the second flow paths 7B. Thereby,the structure of the body 5 can be simplified with one entrance of thecutting oil into the body 5.

It is appropriate to open each second supply port 8B on the outerperiphery of the body 5 in order to supply sufficient amount of thecutting oil to the clearance gap formed between the guide bush 3 and thebody 5. In particular, it is appropriate to form the second flow paths7B and the second supply ports 8B so that the central axes of holes,which forms the second flow paths 7B and the second supply ports 8B, aredirected toward interior surface of the guide bush 3.

Therefore, for example, the second supply port 8B can be opened on theouter periphery of the body 5 by forming the flow path 7 parallel to thetool axis and branching the second flow path 7B in the directionperpendicular to the tool axis. When the central axis of the second flowpath 7B is made perpendicular to the tool axis, processing for formingthe second flow path 7B in the body 5 becomes easy.

Alternatively, the second flow path 7B oblique toward the workpiece Wside may be formed in the body 5 so that the cutting oil promptlypermeates the workpiece W side through the clearance formed between theguide bush 3 and the body 5. Therefore, the second flow path 7B can alsobe formed in the body 5 so that an angle formed between the central axisof the second flow path 7B and the tool axis becomes not less than 10degrees and not more than 90 degrees. When flutes for discharging chipsare formed in the body 5, the second supply port 88B may be opened in aflute or in a margin portion formed between the flutes.

As long as oil film of the cutting oil is formed, lubrication betweenthe guide bush 3 and the body 5 can be fully obtained. On the otherhand, the cutting oil supplied toward the workpiece W from the firstsupply ports 8A formed in the cutting edge part 6 is used for thepurpose of discharging chips, reducing cutting resistance, cooling orthe like.

Therefore, while most of the cutting oil is supplied to the workpiece Wfrom the first supply ports 8A, supplying a minute amount of the cuttingoil to the second supply port 8B or the second supply ports 8B leads toeffective use of the cutting oil. Accordingly, it is preferable to formthe flow paths 7 inside the body 5 so that the quantity of the cuttingoil supplied to the second supply port 8B or the second supply ports 8Bis less than the quantity of the cutting oil supplied to the firstsupply ports 8A. For that reason, the single second supply port 8B maybe formed as shown in the figures, for example. Thereby, the structureof the body 5 can be simplified with allocating appropriate amounts ofthe cutting oil. Note that, a plurality of the second supply ports 8Bmay be formed on the body 5 in order to obtain a sufficient amount ofsupply of the cutting oil to the space between the guide bush 3 and thebody 5 regardless of drilling conditions.

When the workpiece W is drilled by the drill 2, the drill 2 is fed outin the tool axis direction with making the body 5 slidably fit to theguide bush 3 as shown in FIG. 2. Therefore, a relative position of thesecond supply port 8B to the guide bush 3 changes. It is desirable tosupply the cutting oil to the space formed between the guide bush 3 andthe body 5 at the latest by the time drilling starts, i.e., until thecutting edges of the drill 2 contact the workpiece W.

For that reason, the second supply port 8B can be formed at the positionwhere the second supply port 8B opens inside the guide bush 3 in thestate that the cutting edge part 6 is not protruding from inside theguide bush 3 as exemplified in FIG. 1. Thereby, the cutting oil can becertainly supplied between the guide bush 3 and the body 5 beforedrilling starts.

When the feeding amount of the drill 2 is longer than the length of theportion of the guide bush 3, which slidably fits the body 5, the secondsupply port 8B is exposed outside the portion of the guide bush 3, whichslidably fits the body 5, as exemplified in FIG. 2. Nevertheless, thelubricity between the guide bush 3 and the body 5 can be maintainedsince oil film of the cutting oil remains between the guide bush 3 andthe body 5 once the cutting oil is supplied between the guide bush 3 andthe body 5.

What is necessary in order to direct the second supply port 8B insidethe guide bush 3 which slidably fits the body 5 as much as possibleafter applying a feed to the drill 2 is to form the second supply port8B at a position where the second supply port 8B opens at the endportion inside the guide bush 3 on the opposite side to the workpiece Wat the time when the tip of the cutting edge part 6 has contacted theworkpiece W. Therefore, when a gap is formed between the guide bush 3and the workpiece W as shown in the figures, a position of the secondsupply port 8B may be determined in consideration of a distance betweenthe guide bush 3 and the workpiece W.

A drilled product can be manufactured by drilling the workpiece W withsupplying the cutting oil using at least the drill 2 and the guide bush3 which have the above-mentioned structures.

As described above, the drilling unit 1 and the drilling method use thedrill 2, used by being inserted in the guide bush 3, without a backtaper and having at least one oil hole for supplying a cutting oilbetween the guide bush 3 and the drill 2.

Effects

According to the drilling unit 1 and the drilling method, the accuracyin drilling can be improved. The reason is as follows.

FIG. 3 shows an example case of drilling using the conventional straightdrill 10 having a back taper and the guide bush 11.

The typical drill 10 has a back taper. The back taper is formed so thatthe drill 10 does not contact with inner walls of a hole even when thedrill 10 expands with heat during drilling. The back taper isstandardized, and the taper which becomes thin toward the direction of ashank is formed in the drill 10 so that the diameter of the drill 10 isthinned by 0.04 mm to 0.1 mm per 100 mm in length.

On the other hand, in the case of using the guide bush 11 with insertingthe drill 10, the more the drill 10 is fed out to the workpiece W, thelarger the gap between the drill 10 and the guide bush 11 becomes. As aresult, the accuracy of positioning of the drill 10 deteriorates and itleads to the degradation of a drilling accuracy.

On the contrary, in the case of the drill 2 without a back taper, evenwhen the drill 2 is fed out with guiding by the guide bush 3, the gapbetween the drill 2 and the guide bush 3 does not become larger. Inaddition, cutting oil is supplied as lubricating oil between the drill 2and the guide bush 3. Therefore, the frictional force between the drill2 and the guide bush 3 can be reduced fully. As a result, even when thedrill 2 without a back taper expands with heat, transmission fit betweenthe drill 2 and the guide bush 3 is maintainable. Thereby, thedeterioration in the accuracy of positioning of the drill 2 can beprevented and drilling quality can be improved.

As mentioned above, candidates of a material of the workpiece W, forwhich drilling quality can be improved, include a metal, such asaluminum or titanium, a composite material, such as CFRP, which consistsof a resin reinforced with a fiber and a laminate material whichconsists of overlapped metal and composite material.

(Second Implementation)

FIG. 4 is an enlarged vertical longitudinal sectional view showing astructure of a body composing a drill according to the secondimplementation of the present invention. FIG. 5 is a right side view ofthe body shown in FIG. 4.

The drilling unit 1A in the second implementation shown in FIG. 4 isdifferent from the drilling unit 1 in the first implementation in thepoint that the second flow path 7B formed in the body 5 composing thedrill 2 is made exchangeable. Other structures and functions of thedrilling unit 1A in the second implementation does not substantiallydiffer from those of the drilling unit 1 in the first implementation.Therefore, only the body 5 composing the drill 2 is illustrated. Then,same signs are attached to the same elements and corresponding elementsand explanation thereof is omitted.

As shown in FIG. 4 and FIG. 5, a through hole having a diameter largerthan that of the second flow path 7B can be formed at the position ofthe body 5 at which the second flow path 7B should be formed, and afemale screw can be formed inside the through hole. On the other hand, acylindrical member 20 of which outer surface forms a male screw andwhich has the second flow path 7B along the center can be fastened tothe female screw formed in the through hole of the body 5. That is, thecylindrical member 20 in which the second flow path 7B is formed can beinserted into the through hole which has been formed in the body 5.

Then, the member 20 can be detached and attached from and to the body 5of the drill 2. In the example shown in FIG. 4 and FIG. 5, a groove fora flat-bladed screwdriver is formed in the end surface in the outside ofthe member 20 so that the member 20 can be easily detached from andattached to the body 5 of the drill 2.

Thereby, preparing the members 20 in which the second flow paths 7B andthe second supply ports 8B having diameters D different from each otherhave been formed allows changing the size of the second flow path 7B andthe second supply port 8B by exchanging one of the members 20 withanother one. In this case, any one of the members 20 forming the secondsupply ports 8B and the second flow paths 7B in different sizesrespectively is to be attached to the body 5 of the drill 2 so that themember 20 can be exchanged.

As a specific example, the member 20 of which the diameter D of thesecond flow path 7B and the second supply port 8B is 0.5 mm and themember 20 of which the diameter D of the second flow path 7B and thesecond supply port 8B is 1 mm may be prepared, and one of them can bechosen in accordance with the drilling conditions. As a matter ofcourse, the member 20 in which the second flow path 7B and the secondsupply port 8B having another diameter D have been formed may beprepared.

When the diameter D of the second flow path 7B and the second supplyport 8B is determined to an appropriate size in accordance with thedrilling conditions, the cutting oil supplied to the flow path 7 of thebody 5 from a drill driving device can be distributed to the first flowpaths 7A and the second flow path 7B with appropriate amounts.Specifically, supplying an excess quantity of the cutting oil to the gapbetween the guide bush 3 and the body 5 from the second supply port 8Bcan be prevented while supplying an insufficient quantity of the cuttingoil to the gap between the guide bush 3 and the body 5 from the secondsupply port 8B can be prevented.

The important drilling conditions which should be taken intoconsideration in determining the diameter D of the second flow path 7Band the second supply port 8B as an appropriate size include a cuttingresistance and an oil pressure of the cutting oil supplied to the drill2 from a drill driving device. Specifically, when the oil pressure ofthe cutting oil supplied to the body 5 of the drill 2 from a drilldriving device is high enough, sufficient quantity of the cutting oilcan be injected towards the workpiece W from the first supply ports 8Aeven when the cutting resistance is large. On the contrary, when thediameter D of the second flow path 7B and the second supply port 8B isset excessively large in the case where the oil pressure of the cuttingoil supplied to the body 5 of the drill 2 from a drill driving device islow and the cutting resistance is large, an excess amount of the cuttingoil may be supplied to the gap between the guide bush 3 and the body 5from the second supply port 8B while the amount of the cutting oilsupplied from the first supply ports 8A to the workpiece W may becomeinsufficient.

As main conditions which influence to the cutting resistance, a depth ofhole to be drilled, a material of the workpiece W, and a material ofcutting edges are mentioned. That is, the cutting resistance changes inaccordance with a depth of hole to be drilled, a material of theworkpiece W, and a material of the cutting edges. Accordingly, thediameter D of the second flow path 7B and the second supply port 8B canbe changed in accordance with a pressure of the cutting oil suppliedfrom a drill driving device to the drill 2, a depth of hole to bedrilled, a material of the workpiece W, and a material of the cuttingedges.

More specifically, when the cutting resistance is small and a supplypressure of the cutting oil from a drill driving device is high, thediameter D of the second flow path 7B and the second supply port 8B canbe made large so that a sufficient quantity of the cutting oil can beled from the second flow path 7B and the second supply port 8B to thegap between the guide bush 3 and the body 5. On the contrary, when thecutting resistance is large and the supply pressure of the cutting oilis low, the diameter D of the second flow path 7B and the second supplyport 8B can be made small so that most part of the cutting oil isprevented from being supplied from the second flow path 7B and thesecond supply port 8B to the gap between the guide bush 3 and the body 5while the amount of the cutting oil supplied from the first supply ports8A to the workpiece W can be secured.

Some drilling examinations can experientially determine a size of thesecond flow path 7B and the second supply port 8B appropriate for everyconditions, such as a pressure of the cutting oil supplied from a drilldriving device to the drill 2, a depth of hole to be drilled, a materialof the workpiece W and a material of the cutting edges.

According to the above-mentioned drilling unit 1A in the secondimplementation, the size of the second flow path 7B and the secondsupply port 8B for supplying the cutting oil to the space between theguide bush 3 and the body 5 can be adjusted. Thereby, the cutting oilsupplied from a drill driving device to the drill 2 can be distributedto a part to be drilled of the workpiece W, and the space between theguide bush 3 and the body 5 with adequate amounts.

When flutes for discharging chips are formed in the body 5 of the drill2, the second flow path 7B and the second supply port 8B may be formedon a flute or a margin of the body 5, similarly to the firstimplementation. Therefore, the through hole and the female screw forinserting the member 20 can also be formed on a flute or margin of thebody 5. Then, the member 20 can be attached to the flute or margin ofthe body 5.

(Third Implementation)

FIG. 6 shows a structure of a drilling unit including a drill accordingto the third implementation of the present invention. FIG. 7 shows astate where the drilling unit shown in FIG. 6 is drilling a workpiece.

The drilling unit 1B in the third implementation shown in FIG. 6 isdifferent from the drilling unit 1A in the second implementation in thepoint that members 20 each forming the second flow path 7B and thesecond supply port 8B can be attached at positions different in the toolaxis direction of the drill 2. Other structures and functions of thedrilling unit 1B in the third implementation does not substantiallydiffer from those of the drilling unit 1A in the second implementation.Therefore, same signs are attached to the same elements andcorresponding elements and explanation thereof is omitted.

As shown in FIG. 6, the through holes and the female screws forinserting the members 20, each forming the second flow path 7B and thesecond supply port 8B, may be formed at plural positions of the body 5different in the tool axis direction. Then, the second flow paths 7B andthe second supply ports 8B can be formed at different positions in thetool axis direction of the drill 2. In the example shown in FIG. 6, themembers 20 are respectively attached to two different positions of thebody 5 in the tool axis direction so that the members 20 can be attachedand detached to and from the body 5.

When the second flow paths 7B and the second supply ports 8B are formedat different positions in the tool axis direction, even after the secondsupply port 8B closest to the cutting edge part 6 has been exposed fromthe space between the guide bush 3 and the body 5, to which the cuttingoil should be supplied, because of the progression of drilling theworkpiece W, the cutting oil can be continuously supplied to the spacebetween the guide bush 3 and the body 5 from another second supply port8B formed at a different position in the tool axis direction.Consequently, the length of the body 5 which can be fed out in the toolaxis direction toward the workpiece W with sliding fit to the guide bush3 by supply of the cutting oil can be increased. As a result, a deephole can be drilled using the guide bush 3 as shown in FIG. 7.

Therefore, the distance between the adjacent second supply ports 8B canbe determined according to a length of the guide bush 3 to whichlubricity to the body 5 should be given. As explained in the firstimplementation, the cutting oil discharged out from each second supplyport 8B remains as an oil film, during a certain length of period, onthe surface of the body 5 and inside of the guide bush 3. Accordingly,it is appropriate to determine the distance between the adjacent secondsupply ports 8B so that an oil film may not break off between the guidebush 3 and the body 5 even when the body 5 is slid relative to the guidebush 3 by sending out the drill 2 in the tool axis direction.

When it is a case where reducing the number of the members 20 is thoughtas important, the second supply ports 8B can be arranged at an intervalat which an oil film would not break off between the guide bush 3 andthe body 5. As a concrete example, the distance between the secondsupply ports 8B can be determined so that the cutting oil discharged outfrom the second supply port 8B adjacent the shank 5A side of the body 5may arrive at the space, to which the cutting oil should be supplied,between the guide bush 3 and the body 5 through the body 5 before thesecond supply port 8B in the cutting edge part 6 side is exposed fromthe space between the guide bush 3 and the body 5.

Alternatively, when it is a case where ensuring the lubricity betweenthe guide bush 3 and the body 5 is thought as important, the distancebetween the second supply ports 8B can be determined so that the secondsupply port 8B adjacent the shank 5A side of the body 5 may arrive atthe space, to which the cutting oil should be supplied, between theguide bush 3 and the body 5 before the second supply port 8B in thecutting edge part 6 side is exposed from the space between the guidebush 3 and the body 5, for example. That is, the distance between thesecond supply ports 8B can be determined to not more than the length inthe tool axis direction of the space, to which the cutting oil should besupplied, between the guide bush 3 and the body 5, i.e., the length ofthe guide bush 3 which slidingly fits to the body 5.

On the other hand, it is enough to form the single second supply port 8Bin the same position in the tool axis direction, as explained in thefirst implementation. Accordingly, forming the single second supply port8B in the same position in the tool axis direction leads tosimplification of the structure of the drill 2 and reduction of amanufacturing cost of the drill 2. Nevertheless, the number of thesecond supply ports 8B formed in the same position in the tool axisdirection may be more than one in order to obtain a sufficient amount ofsupply of a cutting oil to the space between the guide bush 3 and thebody 5 regardless of drilling conditions.

In the case of enabling it to form the second supply ports 8B atdifferent positions in the tool axis direction, the second supply port Bin the shank 5A side of the body 5 may become unnecessary for drilling ashallow hole. Accordingly, a plug member for blockading the second flowpath 7B and the second supply port 8B may be inserted to the throughhole and the female screw which have been formed in the body 5, insteadof the member 20 for forming the second flow path 7B and the secondsupply port 8B.

FIG. 8 is a longitudinal sectional view of the body 5 showing an examplecase where the through hole for inserting the member 20 shown in FIG. 6is blockaded with the plug member 21.

As exemplified in FIG. 8, when the columnar plug member 21 of which amale screw has been formed on the outer circumference is produced, theplug member 21 can be attached and detached to and from the body 5.Thereby, the second flow path 7B and the second supply port 8B can beblockaded by fastening the male screw of the plug member 21 to thefemale screw formed in the through hole for insertion of the member 20,as necessary, such as a case of drilling a shallow hole. As a result,supply of useless cutting oil can be reduced.

The plug member 21 which blockades the second flow path 7B and thesecond supply port 8B can be also used to the drill 2 in the secondimplementation. When the second flow path 7B and the second supply port8B which can be formed in the drill 2 in the second implementation areblockaded by the plug member 21, the drill 2 can be used even in thecase of drilling without using the guide bush 3. Namely, flexibility canbe given to the drill 2.

Next, an example case where the drilling unit 1B is composed by aninsert drill of which cutting edges can be exchanged will be described.

FIG. 9 is a longitudinal sectional view showing an example case wherethe drilling unit 1B is composed by an insert drill 2A of which body 5has helical flutes and cutting edges can be exchanged. FIG. 10 is alongitudinal sectional view showing a state where the drilling unit 1Bshown in FIG. 9 is drilling a workpiece W. FIG. 11 is an enlargedvertical longitudinal sectional view near the tip of the insert drill 2Ashown in FIG. 9. FIG. 12 is a longitudinal sectional view showing anexample of structure in the cutting edge part 6A of the insert drill 2Ashown in FIG. 9.

As exemplified in FIG. 9 to FIG. 12, the drilling unit 1B can becomposed of the insert drill 2A. The structure of the cutting edge part6A of the insert drill 2A can be made to the structure in which thewidth of the slit 31 can be changed by fastening the bolt 30 as shown inFIG. 12, for example. Specifically, when the bolt 30 is fastened to makethe width of the slit 31 narrow, the cutting edge 32 can be inserted andheld by the cutting edge part 6A. On the contrary, when the bolt 30 isloosened to make the width of the slit 31 expanded, the cutting edge 32can be removed from the cutting edge part 6A.

Such structure of the cutting edge part 6A including one having oilholes is already put into practical use, and can be manufactured easily.Then, the drilling unit 1B can be configured by the insert drill 2A ofwhich the cutting edge part 6A and the body 5 function as a holder ofthe cutting edge 32.

In the example shown in FIG. 9 and FIG. 10, the body 5 of the insertdrill 2A on which helical flutes have been formed has the six secondflow paths 7B and the six second supply ports 8B. Specifically, the twosecond flow paths 7B and the two second supply ports 8B are formed ateach of three positions different in the tool axis direction.Accordingly, a deep hole can be processed using the insert drill 2A. Thesecond flow path 7B and the second supply port 8B can be formed in anyof a flute portion and a margin portion, as exemplified in FIG. 9 andFIG. 10.

The insert drill 2A can be used with being attached to a handheld drilldriving device 40. In the example shown in FIG. 9 and FIG. 10, the malescrew 2B is formed in the back end side of the insert drill 2A so thatthe male screw 2B of the insert drill 2A is fasten to the female screw41 which has been formed in the handheld drill driving device 40,thereby the insert drill 2A is held by the drill driving device 40.

The drill driving device 40 has the cylindrical nosepiece 42 whichshields the insert drill 2A, and the nosepiece 42 is connected with theguide bush 3. Specifically, the male screw which has been formed on theexternal surface of the guide bush 3 is fasten to the female screw whichhas been formed inside of the tip side of the nosepiece 42, thereby thenosepiece 42 is connected with the guide bush 3.

Therefore, not only the insert drill 2A and the guide bush 3 but thehandheld drill driving device 40 having the nosepiece 42 which has astructure connectable to the guide bush 3 may be an element of thedrilling unit 1B. This is the same in the first implementation and thesecond implementation.

According to the drilling unit 1B in the above mentioned thirdimplementation, the second flow paths 7B and the second supply ports 8Bcan be formed at different positions in the tool axis direction of thedrill 2 so that a deep hole can be processed. Moreover, the second flowpath 7B and the second supply port 8B can also be blockaded by the plugmember 21 so that a shallow hole can also be processed.

(Fourth Implementation)

FIG. 13 is a perspective view showing the first structural example of amember inserted into at least one through hole formed in a body of adrill according to the fourth implementation of the present invention.FIG. 14 is a perspective view showing the second structural example of amember inserted into at least one through hole formed in a body of adrill according to the fourth implementation of the present invention.

The drilling unit 1C in the fourth implementation shown in FIG. 13 orFIG. 14 is different from each of the drilling unit 1, the drilling unit1A and the drilling unit 1B in the other implementations in the pointthat the respective pressure losses of the second flow paths 7B formedin the body 5 of the drill 2 are determined so that the cutting oil maybe exuded from the second supply ports 8B formed on the outer peripheralsurface of the body 5 as the outlets of the second flow paths 7Brespectively without being scattered from the second supply ports 8B inthe radial direction of the body 5. Other structures and functions ofthe drilling unit 1C in the fourth implementation do not substantiallydiffer from those of the drilling unit 1, the drilling unit 1A and thedrilling unit 1B in the other implementations. Therefore, only a member20A, a member 20B and a member 20C each forming the second flow path 7Bare illustrated. Then, the same signs are attached to the same elementsand the corresponding elements, and explanation thereof is omitted.

The pressure loss of each second flow path 7B becomes larger as the areaof the cross section is smaller since the frictional resistance with thecutting oil increases. Thus, the cross section area of at least a partof each second flow path 7B can be determined so that the pressure lossof the second flow path 7B becomes one with which the cutting oil isexuded without being scattered from the second supply port 8B in theradial direction of the body 5.

As a practical example, the pressure loss of each second flow path 7Bcan be increased by inserting the column-shaped member 20A, made of aporous material as exemplified in FIG. 13, in a hole reaching the firstflow path 7A from the outer surface of the body 5. Specifically, formingat least a part of each second flow path 7B with a porous material makesit possible to make the pressure loss of each second flow path 7B be apressure loss by which the cutting oil is not scattered from the secondsupply port 8B in the radial direction of the body 5 but exuded from thesecond supply port 8B.

Concrete examples of porous material include porous aluminum in additionto felt (a non-woven fabric), pumice stone and the like. In particular,when porous aluminum of which workability and wear resistance arepreferable is used, it becomes easy to produce the member 20 A, whichforms the second flow path 7B, and attach the member 20 A to the body 5.

As another concrete example, the member 20 B forming the second flowpath 7B whose cross section area has been adjusted as exemplified inFIG. 14 may also be inserted in each through hole formed in the body 5,similarly to the second implementation. Although FIG. 14 shows anexample case where a slit having a rectangular cross section has beenformed, as the second flow path 7B, in the member 20 B, the second flowpath 7B having a circular cross section may be formed in the member 20B. Alternatively, the second flow path 7B having an adjusted crosssection area may be formed directly in the body 5, similarly to thefirst implementation.

When a male screw is formed in the outer surface of the member 20 B andfastened to a female screw formed in each through hole of the body 5,similarly to the second implementation, the member 20 B forming thesecond flow path 7B can be exchanged. Therefore, the plurality of themembers 20 B respectively forming the second flow paths 7B havingpressure losses different from each other may be prepared so that one ofthe members 20 B can be interchangeably attached to the body 5. When aslit is the second flow path 7B as exemplified in FIG. 14, a directionof the slit may also be changed. Accordingly, a direction of a slitand/or the size of the second flow path 7B may be changed according tocutting conditions, such as a supply pressure and a kind of the cuttingoil, the size and rotation speed of the drill 2, a material of theworkpiece W and a depth of a hole to be drilled.

Some actual drilling examinations under various conditions revealed thefollowing fact. A condition that the maximum width of the cross sectionof at least a part of the second flow path 7B is not more than 0.5 mm isimportant in order to prevent the cutting oil from scattering from thesecond supply port 8B in the radial direction of the body 5 even whenthe body 5 is rotated while the cutting oil is supplied to the flow path7 in the body 5. Therefore, it is appropriate that each second flow path7B is a small clearance of which inside diameter or width is about notmore than 0.5 mm.

For that reason, the columnar member 20 which is not hollow and has amale screw on the outer surface, like the plug member 21 shown in FIG.8, may be fastened to a female screw formed in each through hole of thebody 5 so that a clearance formed between the male screw formed on thecolumnar member 20 and the female screw formed in each through hole ofthe body 5 can be used as the second flow path 7B.

FIG. 15 is an enlarged partial sectional view of the body 5 and thecolumnar member 20C, showing an example in which a clearance formedbetween a male screw and a female screw is used as the second flow path7B.

As shown in FIG. 15, a male screw 50A can be formed on the outer surfaceof the columnar member 20C while a female screw 50B can be formed ineach through hole of the body 5. When the male screw 50A formed on thecolumnar member 20C is fastened to the female screw 50B formed in athrough hole of the body 5, a clearance, called a crest clearance of themale screw 50A, is formed between the thread of the male screw 50A andthe root of the female screw 50B while a clearance, called a rootclearance of the male screw 50A, is formed between the root of the malescrew 50A and the thread of the female screw 50B, as long as toleranceclasses of the male screws 50A and the female screw 50B are typicalrespectively.

Accordingly, each of the clearances formed between the male screw 50Aand the female screw 50B can be used as the second flow path 7B fordischarging and exuding the cutting oil from the body 5. In this case,the second flow path 7B become spiral and the width of the second flowpath 7B can be adjusted by selecting tolerance classes of a male screwand a female screw which classify fitting between the male screw and thefemale screw into classifications including precise, middle and rough.

On the contrary, when the second flow path 7B is blockaded by the plugmember 21 shown in FIG. 8, it is important to adopt a specification of apair of screws in which a clearance from which the cutting oil may leakis not generated between the male screw formed on the plug member 21 andthe female screw formed in each through hole of the body 5, similarly toa case using a pipe thread.

In addition to the above-mentioned example, at least one of central axesof the second flow paths 7B may be slanted in the workpiece W side sothat the cutting oil may be discharged not in the rotating radialdirection of the body 5 but toward the workpiece W side. Moreover, it isexperientially important to form the flow paths 7 so that the amount ofthe cutting oil supplied to the first supply ports 8A formed as theoutlets of the first flow paths 7A respectively becomes not less thantwice the amount of the cutting oil supplied to the second supply ports8B formed as the outlets of the second flow paths 7B respectively, froma viewpoint of avoiding shortage in the cutting oil which should besupplied to the first flow paths 7A and the first supply ports 8A, as aresult that an excess amount of the cutting oil has been supplied to thesecond flow paths 7B and the second supply ports 8B.

According to the drilling unit 1C in the above-mentioned fourthimplementation, it can be prevented that an excess amount of the cuttingoil is supplied to the second flow paths 7B and the second supply ports8B. As a result, it becomes possible to prevent the cutting oil fromscattering from the second supply ports 8B which have been exposed tothe outside of the guide bush 11. Alternatively, the amount of thecutting oil scattering from the second supply ports 8B which have beenexposed to the outside of the guide bush 11 can be reduced.

On the other hand, a sufficient amount of the cutting oil can besupplied to the first flow paths 7A and the first supply ports 8A. Thatis, a pressure of the cutting oil supplied to the first flow paths 7Aand the first supply ports 8A can be secured since a pressure loss dueto scattering of the cutting oil from the second supply ports 8B can beremarkably reduced.

Moreover, cleaning work after drilling of the workpiece W becomes easysince the cutting oil scattering from the second supply ports 8B can beeliminated or at least an amount of the cutting oil scattering from thesecond supply ports 8B can be decreased.

(Other Implementations)

While certain implementations have been described, these implementationshave been presented by way of example only, and are not intended tolimit the scope of the invention. Indeed, the novel methods and systemsdescribed herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the invention. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the invention.

What is claimed is:
 1. A drill comprising: a body without a back taper,the body having a flow path of a cutting oil inside, the flow path beingbranched to a first flow path and a second flow path inside the body;and a cutting edge part integrated with the body, the cutting edge parthaving a first supply port that supplies the cutting oil toward aworkpiece, the first supply port being an outlet of the first flow path,wherein the body has a second supply port that supplies the cutting oilto a clearance formed between the body and a bush for positioning thebody, the bush being used by inserting the body inside the bush, thesecond supply port being an outlet of the second flow path, the outletof the second flow path being formed on an outer peripheral surface ofthe body, the second flow path having a pressure loss by which thecutting oil is not scattered from the second supply port in a radialdirection of the body but exuded from the second supply port.
 2. Thedrill according to claim 1, wherein a cross section of at least a partof the second flow path has an area causing the pressure loss.
 3. Thedrill according to claim 1, wherein at least a part of the second flowpath has been formed by a porous material or a clearance between a malescrew and a female screw, the porous material or the clearance betweenthe male screw and the female screw causing the pressure loss.
 4. Thedrill according to claim 1, wherein the first flow path supplies a firstquantity of the cutting oil to the first supply port while the secondflow path supplies a second quantity of the cutting oil to the secondsupply port, the first quantity being not less than twice the secondquantity.
 5. The drill according to claim 1, wherein the body and thecutting edge part form a holder that holds at least one cutting edgeinterchangeably.
 6. The drill according to claim 1, wherein a diameterof the cutting edge part is larger than a diameter of the body in acutting edge part side.
 7. The drill according to claim 1, whereinmembers forming second supply ports having different pressure lossesrespectively have been interchangeably attached to the body.
 8. Adrilling unit comprising: the drill according to claim 1; and the bush.9. A drilling unit comprising: the drill according to claim 5; and thebush, wherein the bush has a step through hole consisting of a firsthole having a first diameter and a second hole having a second diametersmaller than the first diameter, the first hole guiding the cutting edgepart in a workpiece side, the second hole guiding the body.
 10. Thedrilling unit according to claim 8, further comprising: a drill drivingdevice having a nosepiece coupled to the bush.
 11. A drilling method forproducing a drilled product comprising: using at least the drillaccording to claim 1 and the bush for drilling the workpiece; andsupplying the cutting oil.
 12. The drill according to claim 2, whereinat least a part of the second flow path has been formed by a porousmaterial or a clearance between a male screw and a female screw, theporous material or the clearance between the male screw and the femalescrew causing the pressure loss.
 13. The drill according to claim 2,wherein the first flow path supplies a first quantity of the cutting oilto the first supply port while the second flow path supplies a secondquantity of the cutting oil to the second supply port, the firstquantity being not less than twice the second quantity.
 14. The drillaccording to claim 3, wherein the first flow path supplies a firstquantity of the cutting oil to the first supply port while the secondflow path supplies a second quantity of the cutting oil to the secondsupply port, the first quantity being not less than twice the secondquantity.
 15. The drill according to claim 2, wherein the body and thecutting edge part form a holder that holds at least one cutting edgeinterchangeably.
 16. The drill according to claim 3, wherein the bodyand the cutting edge part form a holder that holds at least one cuttingedge interchangeably.
 17. The drill according to claim 2, wherein adiameter of the cutting edge part is larger than a diameter of the bodyin a cutting edge part side.
 18. The drill according to claim 3, whereina diameter of the cutting edge part is larger than a diameter of thebody in a cutting edge part side.
 19. The drill according to claim 2,wherein members forming second supply ports having different pressurelosses respectively have been interchangeably attached to the body. 20.The drill according to claim 3, wherein members forming second supplyports having different pressure losses respectively have beeninterchangeably attached to the body.